I've always been "underweight" according to the body mass index but, it isn't a eating disorder thing. It is a genetic, metabolism, muscle mass, figety weirdo, body type thing. Weight gain isn't always a calorie thing especially with medication. My main concern with medication has been weight loss.

Zoloft, Prozac and Celexa had me losing weight,though they are generally weight neutral, generally they don't cause mania either haha. Wellbutrin which I'm on now, makes eating during the day the most annoying chore!

I take Seroquel which makes me so hungry at night I love it! No weight gain though. And lamotrigine, which is supposed to be weight neautral right?

I don't think any of the atypical antipsychotics are weight neutral. Perhaps mix a weight neutral mood stabalizer like lamictal with a low dosage antipsychotic?

Of course if you need a high dosage antipsychotic over a long period, that really sucks! For more than just weight gain issues, sigh. They're always testing out new drugs on people. An antipsychotic with no weight gain would lead to a very generous profit. Don't think they're not looking!